there are actually hundreds i believe. in the opening songs of the 1st season, they have this one point where they show a bunch of girls wearin ritual-like clothing with the geass symbol on their forheads.

marianne is a witch? if she was a witch, she wouldn't die!!!!

*sigh* use spoiler tag please

oh and in a spoiker in second season they said

Spoiler Alert! Click to show or hide

Marianne is alive
shes the strongest in their clan

and to answer this thread, theres a lot of witches out there but their in hiding and C.C. knows them all ^_^
she can even talk to them, and if you would watch and listen carefully, one of them is a peeping tom because that witch always wants to see kallen naked xDD LOL

Yes, VV's a boy. So can't really call him a Witch. Maybe Wizard or Warlock.

why does he look like a girl?

I don't know. That's just how they designed him. I'm guessing all immortals like having their hair long.

Uhmm.. if V.V is a boy then the emperor kissed him right???
Barf!!!!1!!!

Ya well, first off how do we know VV's a guy? Second off, for the initial poster, only two known witches have been revealed but the teasers within the anime suggest there may be or may have been more witches.